jackson-core — security advisory
The non-blocking (asynchronous) JSON parser in jackson-core does not enforce the maxNumberLength constraint defined in StreamReadConstraints (default: 1000 characters). An attacker able to submit JSON to an application that uses the async parser API can supply a number token of arbitrary length, leading to excessive memory allocation and potential CPU exhaustion, resulting in a denial of service. The synchronous parser enforces this limit correctly, so the constraint is applied inconsistently depending on which parsing API the application uses. Root cause: the async parsing path in NonBlockingUtf8JsonParserBase and related classes never invokes the number length validation methods. Number parsing methods such as _finishNumberIntegralPart() accumulate digits into the TextBuffer without any length check, then call _valueComplete() to finalize the token. _valueComplete() does not call resetInt() or resetFloat(), which are the methods in ParserBase where validateIntegerLength() and validateFPLength() are performed. Because that validation step is skipped, maxNumberLength is never enforced on the async code path. Impact: an attacker sending a JSON document containing an arbitrarily long number to an application using the async parser (for example a Spring WebFlux or other reactive application) can cause unbounded allocation in the TextBuffer and an OutOfMemoryError. If the application subsequently calls getBigIntegerValue() or getDecimalValue(), the JVM may additionally be tied up
- Products
- jackson-core
- Affected versions
- 2.10.0-1, 2.10.1-1, 2.12.1-1, 2.13.0-1, 2.13.0-2, 2.14.1-1, 2.14.1-1build1, 2.14.1-2, 2.4.2-2, 2.8.6-1, 2.9.1-1, 2.9.4-1, 2.9.8-3, 2.9.8-3~18.04
- Fixed versions
- Not specified
- CVEs
- CVE-2026-18401
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 02:55 UTC · Revision 1
Source evidence
The non-blocking (asynchronous) JSON parser in jackson-core does not enforce the maxNumberLength constraint defined in StreamReadConstraints (default: 1000 characters). An attacker able to submit JSON to an application that uses the async parser API can supply a number token of arbitrary length, leading to excessive memory allocation and potential CPU exhaustion, resulting in a denial of service. The synchronous parser enforces this limit correctly, so the constraint is applied inconsistently depending on which parsing API the application uses. Root cause: the async parsing path in NonBlockingUtf8JsonParserBase and related classes never invokes the number length validation methods. Number parsing methods such as _finishNumberIntegralPart() accumulate digits into the TextBuffer without any length check, then call _valueComplete() to finalize the token. _valueComplete() does not call resetInt() or resetFloat(), which are the methods in ParserBase where validateIntegerLength() and validateFPLength() are performed. Because that validation step is skipped, maxNumberLength is never enforced on the async code path. Impact: an attacker sending a JSON document containing an arbitrarily long number to an application using the async parser (for example a Spring WebFlux or other reactive application) can cause unbounded allocation in the TextBuffer and an OutOfMemoryError. If the application subsequently calls getBigIntegerValue() or getDecimalValue(), the JVM may additionally be tied up
osv:UBUNTU-CVE-2026-18401
jackson-core
Fixed versions: Not specified
jackson-core
Fixed versions: Not specified
jackson-core
Fixed versions: Not specified
jackson-core
Fixed versions: Not specified
jackson-core
Fixed versions: Not specified
jackson-core
Fixed versions: Not specified
jackson-core
Fixed versions: Not specified
Complete source record
{
"id": "b6f0199f25c9873d911d09973ff79691e8f7a314cc402f06e4feffafd7c4ed90",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-18401",
"method": "structured",
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"title": "UBUNTU-CVE-2026-18401",
"summary": "The non-blocking (asynchronous) JSON parser in jackson-core does not enforce the maxNumberLength constraint defined in StreamReadConstraints (default: 1000 characters). An attacker able to submit JSON to an application that uses the async parser API can supply a number token of arbitrary length, leading to excessive memory allocation and potential CPU exhaustion, resulting in a denial of service. The synchronous parser enforces this limit correctly, so the constraint is applied inconsistently depending on which parsing API the application uses. Root cause: the async parsing path in NonBlockingUtf8JsonParserBase and related classes never invokes the number length validation methods. Number parsing methods such as _finishNumberIntegralPart() accumulate digits into the TextBuffer without any length check, then call _valueComplete() to finalize the token. _valueComplete() does not call resetInt() or resetFloat(), which are the methods in ParserBase where validateIntegerLength() and validateFPLength() are performed. Because that validation step is skipped, maxNumberLength is never enforced on the async code path. Impact: an attacker sending a JSON document containing an arbitrarily long number to an application using the async parser (for example a Spring WebFlux or other reactive application) can cause unbounded allocation in the TextBuffer and an OutOfMemoryError. If the application subsequently calls getBigIntegerValue() or getDecimalValue(), the JVM may additionally be tied up",
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"modified": "2026-10-17T12:59:53.549885290Z",
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"references": [
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"https://www.cve.org/CVERecord?id=CVE-2026-18401",
"https://github.com/FasterXML/jackson-core/security/advisories/GHSA-72hv-8253-57qq",
"https://github.com/FasterXML/jackson-core/pull/1555",
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